Fasciolosis is a worldwide zoonotic infection caused by liver flukes of the genus Fasciola, of which Fasciola hepatica and a larger species, Fasciola gigantica are the most common representatives. These two food-borne trematodes usually infect domestic ruminants and cause important economic losses to sheep, goats and cattle. In commercial herds, fasciolosis is of great economic significance worldwide with losses estimated to exceed 2000 million dollars yearly, affecting more than 600 million animals, in articles reported a decade ago. In addition, F. hepatica causes an estimated loss of $3 billion worldwide per annum through livestock mortality, especially in sheep, and by decreased productivity via reduction of milk and meat yields in cattle. The parasitological diagnosis of fasciolosis is often unreliable because the parasite’s eggs are not found during the prepatent period. Even when the worms have matured, the diagnosis may still be difficult since eggs are only intermittently released. Repeated examinations of stools are usually required to increase the accuracy of the diagnosis. Early diagnosis of fasciolosis is necessary for institution of prompt treatment before irreparable damage of the liver occurs. For these reasons, serology is the most dependable method for diagnosing fasciolosis. Attempts have been made to diagnose fasciolosis by detecting antibodies in the serum of sheep suspected of being infected with the flukes. Advances in immunodiagnosis have focused on detection of Fasciola antigens in host body fluid; these tests have an advantage over antibody detection because antigenemia implies recent and active infection. Similarly, somatic and excretory secretory (E/S) antigens of Fasciola sp. or their partially purified component are the commonest source of antigens used in protection trials and serodiagnosis. Thus, the aim of the present review is to encourage more young researchers to initiate work on this aspect of these economically cosmopolitan parasites.